This invention relates to a combustion chamber for a spark ignited engine and more particularly to a combustion chamber that promotes rapid flame travel through the use of a squish area and which nevertheless offers economy of construction.
It is well known that one way of avoiding the phenomenon known as "knocking" in an internal combustion engine is to cause the flame propagation in the combustion chamber to occur more rapidly. One of the main causes of knocking is slow flame travel which results in auto ignition in the remote areas of the combustion chamber. Flame propagation may be accelerated through the use of various turbulence inducing devices in the combustion chamber. One of the most widely utilized turbulence inducing arrangements utilizes a squish area. The squish area is a restricted area between the head of the piston and the adjacent surface of the cylinder head. As the piston approaches its top dead center position, the fuel/air mixture in the squish area is squeezed from this area and injected at a high velocity into the larger volume of the combustion chamber. As should be readily apparent, the more restricted the height of the squish area, the greater its effect.
There are, however, certain practical limits to the amount of reduction possible in the squish area height. For example, the squish height may be reduced through a thinning of the cylinder head gasket. However, thin cylinder head gaskets can cause problems in failing to provide effective sealing. In addition, the thin gaskets are prone to failure.
Another way that the squish height may be reduced is by forming a raised area on the head of the piston that extends above the cylinder bore. When this is done, however, the piston will extend into the area where the cylinder head gasket lies. As a result, it is necessary to accurately locate the bore diameters of the cylinder head gasket and to insure an accurate location of the cylinder head gasket upon assembly so as to avoid interference with the piston head. The use of such high tolerances and careful assembly techniques can add significantly to the cost of the engine, however.
It is, therefore, a principal object of this invention to provide an improved combustion chamber configuration for an internal combustion engine.
It is a further object of this invention to provide a combustion chamber configuration that affords a high squish action but which avoids the disadvantages aforenoted.
It is a further object of this invention to provide a combustion chamber configuration for an internal combustion engine that has a high squish area and which is able to achieve this without the use of thin cylinder head gaskets or high tolerances and complicated manufacturing techniques.